The vast majority of us—if not absolutely everyone—have heard of the great Greek mathematician and philosopher Pythagoras. He is widely regarded as one of the earliest figures in the history of pure mathematics and as a thinker whose ideas influenced generations of mathematicians and philosophers who followed him.

From our earliest years in school, we are taught that Pythagoras is best known for discovering the Pythagorean Theorem. This fundamental principle of geometry states that in any right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides.

The Pythagorean Theorem is commonly expressed with the formula:
a² + b² = c².
This equation is not merely an abstract mathematical idea; it has countless real-world applications. It is used to calculate inaccessible distances, plays a critical role in architectural design and construction, supports navigation and map-making, and helps solve a wide range of practical and theoretical problems across science and engineering.

But what if it turns out that this theorem existed long before Pythagoras himself?

Archaeologists have discovered a Babylonian clay tablet on which this mathematical relationship appears to be explained—one that predates Pythagoras by nearly 1,000 years. The tablet, known as IM 67118, is currently housed in the Iraq Museum. It was uncovered in 1962 at Tell edh-Dhiba’i, an ancient Babylonian settlement near present-day Baghdad.

This clay tablet, likely used for teaching purposes, dates back to around 1770 BCE, centuries before Pythagoras was born in approximately 570 BCE. Originating from the Old Babylonian period, it contains mathematical content related to geometric–algebraic theory, particularly involving right triangles, in a manner strikingly similar to later Euclidean geometry.

According to mathematician Bruce Ratner, who discussed this artifact in an article published by Springer, “The conclusion is unavoidable. The Babylonians knew the relationship between the length of the diagonal of a square and its side: d = √2.” Ratner further explains that this was likely the first number known to be irrational. This knowledge strongly suggests that the Babylonians were familiar with the Pythagorean Theorem—or at least with its special case involving the diagonal of a square, expressed as d² = a² + a² = 2a²—more than a millennium before the great sage whose name the theorem bears.

Given this evidence, an important question arises: why is the discovery still attributed to Pythagoras?

In reality, there are no surviving written records directly authored by Pythagoras himself that prove he discovered the theorem. His teachings were passed down orally within the Pythagorean school in Magna Graecia and preserved by members of the Pythagorean brotherhood. Over time, these ideas endured through tradition rather than documentation, ultimately becoming inseparable from Pythagoras’s legacy.

As a result, while the mathematical knowledge may have existed long before him, history has immortalized Pythagoras as the figure most closely associated with this timeless theorem—demonstrating how influence, transmission, and legacy can shape our understanding of discovery just as much as invention itself.